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ARS Home » Northeast Area » University Park, Pennsylvania » Pasture Systems & Watershed Management Research » Research » Publications at this Location » Publication #179059
Title: INSITU MEASUREMENTS OF NITRATE LEACHING IMPLICATE POOR NITROGEN AND IRRIGATION MANAGEMENT ON SANDY SOILS

Author
item GEHL, R - KANSAS STATE UNIV
item Schmidt, John
item STONE, L - KANSAS STATE UNIV
item SCHLEGEL, A - KANSAS STATE UNIV
item CLARK, G - KANSAS STATE UNIV

Submitted to: Journal of Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/6/2005
Publication Date: 11/7/2005
Citation: Gehl, R.J., Schmidt, J.P., Stone, L.R., Schlegel, A.J., Clark, G.A. 2005. Insitu measurements of nitrate leaching implicate poor nitrogen and irrigation management on sandy soils. Journal of Environmental Quality. 34:2243-2259.

Interpretive Summary: Minimizing the risk of nitrate (NO3) contamination of groundwater along the rivers of the Great Plains, USA, will be essential to continued irrigated corn production and quality drinking water supplies in this region. This study quantified NO3 leaching for an irrigated sandy soil along the Arkansas River Valley, representing the leaching potential of many sandy soils in this region. Maximum corn grain yield was achieved with nitrogen (N) rates between 110 and 165 lb N per acre for two irrigation schedules (100% and 125% of recommended rates, noted as 1X and 1.25X IS, respectively). The 1.25X IS exacerbated the amount of NO3 leached below the 5-ft depth for preplant N treatments, averaging 130 lb N per acre lost during the growing season when 220 and 270 lb N per acre were applied preplant compared with 10 lb N per acre lost for the same N treatments but less irrigation (1X IS). When 165 lb N per acre was applied, the 1.25X IS treatment resulted in 66 lb N per acre lost compared with 9 lb N per acre for the 1X IS. Maximum daily NO3-N flux occurred on 23 July 2002 for the 1.25X IS, when 3.2 lb N per acre per day leached below 5 ft (averaged across all N treatments), corresponding to a period of increased water flux and increased soil water NO3 concentration. Results from this study emphasize the importance of combining sound irrigation and N management strategies for corn production. Most important is to apply N fertilizer rates that match crop requirements; however, even when N fertilizer rates are appropriate, but irrigation rates are in excess of requirements, NO3 is moved below the root zone and represents a risk to groundwater.

Technical Abstract: Minimizing the risk of nitrate contamination along the tributaries of the Great Plains, USA, will be essential to continued irrigated corn production and quality drinking water supplies in this region. The objectives of this study were to quantify nitrate (NO3) leaching potential for the irrigated sandy soils along the Arkansas River Valley and to evaluate the effects of current and alternative N and water management strategies on NO3 leaching potential in irrigated corn. Two irrigation schedules (1X and 1.25X optimum) were combined with 6 N fertilizer treatments broadcast as NH4NO3 (kg N ha-1): 300 and 250 applied pre-plant; 250 applied pre-plant and sidedress; 185 applied pre-plant and sidedress; 125 applied pre-plant and sidedress; and 0. Porous-cup tensiometers and solution samplers were installed in each of the four highest N treatments. Water samples were collected during the 2001 and 2002 growing seasons. Maximum corn grain yield was achieved with 125 or 185 kg N ha-1, regardless of the irrigation schedule (IS). The 1.25X IS exacerbated the amount of NO3 leached below the 152-cm depth in the preplant N treatments, with a mean of 146 kg N ha-1 for the 250 and 300 kg N preplant applications compared with 12 kg N ha-1 for the same N treatments but 1X IS. With 185 kg N ha-1, the 1.25X IS treatment resulted in 74 kg N ha-1 leached compared with 10 kg N ha-1 for the 1X IS. Maximum daily NO3-N flux occurred on 23 July 2002 for the 1.25X IS, when 3.6 kg N ha-1 d-1 leached below 152 cm (averaged across all N treatments), corresponding to the period of increased water flux and soil water NO3-N concentrations. Appropriate irrigation scheduling and N fertilizer rates are essential to best N management practices on these sandy soils.